Simulation Of Groundwater Flow Research Articles

3D-Mathematical model to simulate groundwater flow and sulfate concentration in Tantaria watershed, Bemetara district, Chhattisgarh, India

3D-Mathematical model to simulate groundwater flow and sulfate concentration in Tantaria watershed, Bemetara district, Chhattisgarh, India

Transmissivity and groundwater flow exert a strong influence on drainage density

Abstract. The extent to which groundwater flow affects drainage density and erosion has long been debated but is still uncertain. Here, I present a new hybrid analytical and numerical model that simulates groundwater flow, overland flow, hillslope erosion and stream incision. The model is used to explore the relation between groundwater flow and the incision and persistence of streams for a set of parameters that represent average humid climate conditions. The results show that transmissivity and groundwater flow exert a strong control on drainage density. High transmissivity results in low drainage density and high incision rates (and vice versa), with drainage density varying roughly linearly with transmissivity. The model evolves by a process that is defined here as groundwater capture, whereby streams with a higher rate of incision draw the water table below neighbouring streams, which subsequently run dry and stop incising. This process is less efficient in models with low transmissivity due to the association between low transmissivity and high water table gradients. A comparison of different parameters shows that drainage density is most sensitive to transmissivity, followed by parameters that govern the initial slope and base level. The results agree with field data that show a negative correlation between transmissivity and drainage density. These results imply that permeability and transmissivity exert a strong control on drainage density, stream incision and landscape evolution. Thus, models of landscape evolution may need to explicitly include groundwater flow.

Development of a Reservoir Simulator to Model Single-Phase Flow in Porous Media

Any groundwater reservoir requires tools to predict future performance as well as to optimize its operation. It is then necessary to simulate groundwater flow in porous media because of the uncertainty and heterogeneity associated with reservoirs. This study developed a reservoir simulator for modeling a single-phase flow in a porous medium. The development of the simulator consists of the physical and mathematical modeling of the reservoir. A MATLAB code was developed to describe groundwater flow in order to appreciate reservoir hydrodynamic pressure distributions from hydraulic head as a function of radial distance while varying the production flow. The formulation equation obtained was solved by the direct method. Examples of graphical plots generated from the simulator illustrate that before the coordinate point P (r=33.74m; h=286.65m) for any value of production flow, hydraulic head or hydrodynamic pressure of the reservoir increases equally with radial distance. This reflects the same drop in the static pressure of the reservoir. Beyond point P, there is a further increase in the hydraulic head, i.e., the hydrodynamic pressure of the reservoir as the production flow increases with the increase in population. This results in a drop in the static pressure of the reservoir in proportion to the increase in the production flow. The variations of the production flow carried out show that the static pressure of the reservoir decreases when the production flow increases. Finally, the simulator to predict the hydraulic head distributions i.e., the hydrodynamic pressure of the reservoir in single-phase flow during production periods is a springboard towards the implementation of multi-phase fluid flow formulations.

Groundwater Recharge Assessment Using WetSpass and MODFLOW Coupling: The Case of Hormat-Golina Sub-basin, Northern Ethiopia

Water scarcity in northern Ethiopia, as well as its socio-economic relevance in terms of water demand for agriculture and domestic use, are at the root of the search for new groundwater resources and the development of groundwater models that can be used to control and manage the resource. The groundwater recharge of the Hormat-Golina sub basin was assessed using WetSpass-MODFLOW coupling. The goal of this paper is to assess the groundwater recharge in the Hormat-Golina sub-basin. These findings are then used to simulate the hydraulic head distribution using the MODFLOW groundwater flow simulation model. By comparing measured and simulated hydraulic heads, the steady state groundwater flow calibration was obtained. WetSpass calculated the mean annual evapotranspiration, surface runoff, and groundwater recharge to be 516.6, 204.9, and 35.6 mm, respectively. Groundwater recharge accounted for 4.7% of precipitation, while actual evapotranspiration and surface runoff accounted for 27% and 68% of precipitation, respectively. In such seasonal variations, the groundwater head distribution is 9.37 to 29.86 m in the winter (dry season), 9.53 to 29.89 m in the summer (wet season), and 9.58 to 30.17 m in the annual stress periods (recharges). For all stress periods, the estimated hydraulic heads in steady state fit well with the measured ones, with a correlation coefficient of 0.86 (summer, winter, and annual recharge). To preserve the resource's long-term viability, the balance between groundwater recharge and projected abstraction rates for agriculture and domestic water supply must be considered in future groundwater resource development plans in the valley.

Modeling, simulation and analysis of groundwater flow captured by the horizontal reactive media well using the cell-based smoothed radial point interpolation method

The Horizontal Reactive Media Treatment (HRX) well is a novel technology for in situ treatment of contaminated groundwater. The most significant technical performance risk associated with field-scale implementation of the HRX well is the potential for water to bypass the well untreated. Therefore, the groundwater capture simulation plays a very important role in the design of the HRX well. We build a model based on a cell-based smoothed radial point interpolation method (CS-RPIM) for simulating groundwater flow captured by the HRX well in both 3D test pit pilot scale and field scale. This method is compared with the finite element method and measured values. Capture width and groundwater velocity obtained by CS-RPIM are consistent with the measured values. We further develop MATLAB software modules to analyze the effects of the hydraulic conductivities, dimension of well and other parameters on the groundwater capture zone, velocity and residence time in the reactive media. The results show that increase of well diameter has a significant effect on enlargement of the capture zone and the extension of media treatment time. When well diameter increases by 100%, horizontal and vertical capture width increase by 57% and 50% respectively, and media treatment time can be extended by 68%.

ANALISIS PENGARUH NILAI KONDUKTIVITAS HIDRAULIK DAN DISPERSIVITAS DINAMIK TERHADAP REMEDIASI AIR TANAH MENGGUNAKAN SIMULASI NUMERIK

Groundwater remediation is one of the solutions to restore the contaminated groundwater. This study was conducted to determine the effect of hydraulic conductivity and dynamic dispersivity on the groundwater remediation effectiveness. As a case study, in 2020, in an area located in Balikpapan, groundwater remediation will be carried out by injecting water containing NaOH through five wells and pumping it back through five wells to form a cycle. The method used is a numerical simulation consisting of groundwater flow simulation, mass transport, and sensitivity analysis. The results show that it takes 124 to 300 days for the injected NaOH to arrive at the pumping wells. The sensitivity analysis results show that when the hydraulic conductivity value is ten times greater, the time required is reduced to 84 to 172 days. Meanwhile, when the dynamic dispersivity is twice larger, the time required is reduced to 75 to 189 days. These results indicate that the groundwater remediation method will be effective for aquifers with high hydraulic conductivity and dynamic dispersivity values. For the study area, the groundwater remediation is suggested to be carried out by increasing the number of injection and pumping wells with a relatively close distance, i.e., around 10 meters, so that NaOH arrives at the pumping wells more quickly.Keywords: groundwater, remediation, hydraulic conductivity, dynamic dispersivity, numerical simulation

An improved numerical model for groundwater flow simulation with MPFA method on arbitrary polygon grids

Groundwater models are critical for simulating subsurface hydrological processes and guiding informed policy-making for groundwater management. However, the widely applied groundwater models typically use regular-shaped grids to discretize aquifer systems and require that the directions of the grid edges are aligned with the hydraulic conductivity tensor. Such rigorous requirements for spatial discretization have constrained the models’ application in aquifer systems with anisotropic hydrogeological characteristics. To address such limitations, we develop an improved groundwater flow model based on the multipoint flux approximation (MPFA) method in this study. The new model allows us to use arbitrary-shaped polygon grids to discretize aquifer systems and relaxes the rigorous requirement of the alliance between polygon edges and hydraulic conductivity tensor. The functionality and performance of the new model are demonstrated by comparing the output between our model, MODFLOW, and analytical solution in four case studies with various hydrogeological conditions. In a real-world watershed with complex-shaped boundaries, our model outperforms the conventional groundwater model in boundaries. The modeling results show that our model can yield accurate simulation of subsurface hydrological processes in aquifer systems with complex-shaped boundaries. Furthermore, our model can provide a more flexible discretization solution to couple surface water and groundwater model in integrated hydrological model development.

Along‐Shore Movement of Groundwater and Its Effects on Seawater‐Groundwater Interactions in Heterogeneous Coastal Aquifers

AbstractStudies of coastal groundwater dynamics often assume two‐dimensional (2D) flow and transport along a shore‐perpendicular cross‐section. We show that along‐shore movement of groundwater may also be significant in heterogeneous coastal aquifers. Simulations of groundwater flow and salt transport incorporating different geologic structure show highly three‐dimensional (3D) preferential flow paths. The along‐shore movement of groundwater on average accounts for 40%–50% of the total flowpath length in both conduit‐type (e.g., volcanic) heterogeneous aquifers and statistically equivalent (e.g., deltaic) systems generated with sequential indicator simulation (SIS). Our results identify a critical role of three‐dimensionality in systems with connected high‐permeability geological features. 3D conduit features connecting land and sea cause more terrestrial groundwater flow through the inland boundary and intensify water exchange along the land‐sea interface. Therefore, conduits increase the rate of SGD compared to equivalent homogeneous, SIS and corresponding 2D models. In contrast, in SIS‐type systems, less‐connected high‐permeability features produce mixing zones and SGD nearer to shore, with comparable rates in 3D and 2D models. Onshore, 3D heterogeneous cases have longer flowpaths and travel times from recharge to discharge compared to 2D cases, but offshore travel times are much shorter, particularly for conduit‐type models in which flow is highly preferential. Flowpath lengths and travel times are also highly variable in 3D relative to 2D for all heterogeneous simulations. The results have implications for water resources management, biogeochemical reactions within coastal aquifers, and subsequent chemical fluxes to the ocean.

Proposing the Optimum Withdrawing Scenarios to Provide the Western Coastal Area of Port Said, Egypt, with Sufficient Groundwater with Less Salinity

Recently, groundwater resources in Egypt have become one of the important sources to meet human needs and activities, especially in coastal areas such as the western area of Port Said, where seawater desalination cannot be used due to the problem of oil spill and the reliance upon groundwater resources. Thus, the purpose of the study is the sustainable management of the groundwater resources in the coastal aquifer entailing groundwater abstraction. In this regard, the Visual MODFLOW and SEAWAT codes were used to simulate groundwater flow and seawater intrusion in the study area for 50 years (from 2018 to 2068) to predict the drawdown, as well as the salinity distribution due to the pumping of the wells on the groundwater coastal aquifer based on field investigation data and numerical modelling. Different well scenarios were used, such as the change in well abstraction rate, the different numbers of abstraction wells, the spacing between the abstraction wells and the change in screen depth in abstraction. The recommended scenarios were selected after comparing the predicted drawdown and salinity results for each scenario to minimize the seawater intrusion and preserve these resources from degradation.

Groundwater flow simulation in a confined aquifer using Local Radial Point Interpolation Meshless method (LRPIM)

Groundwater flow problems are generally solved using analytical or numerical methods. Though analytical solutions are exact and preferable, they are not available for complex field problems. Hence numerical methods such as Finite Element and Finite Difference methods are used to solve complex groundwater problems. These conventional mesh/ grid-based numerical methods need construction of a detailed mesh/ grid. On the other hand, the meshless approach creates a system of algebraic equations on a collection of distributed nodes in the problem area and the boundary. As a result, it is easy to incorporate any modifications to the model at a later time by simply adding nodes to the domain. In this study a weak form meshless method known as local radial point interpolation method (LRPIM) which uses radial basis functions for approximation or interpolation is developed to solve the groundwater flow problems in a confined aquifer. The results obtained from the LRPIM model has been compared with other numerical methods for benchmark and real field problems, and are found to be satisfactory. Implementation of the essential boundary conditions was relatively easier in LRPIM and gave good accuracy for the problems considered. LRPIM can potentially be used as an alternative to the other conventional methods, especially where the domain boundary is irregular or varying with time.

Modelling transient discharge into deep-buried tunnels in karst area based on a coupled discrete-continuum model

Karst aquifers are characteristic of complex hydrogeological conditions and highly developed void structures, often causing serious water and mud inrush, karst collapse and other geological disasters during construction of deep-buried tunnels. Accurate prediction of groundwater discharge into tunnels has become a key issue for tunnel engineering in karst formations. Motivated by safety assessment of tunnel construction in the Jiayan Water Diversion Project located in Guizhou Province, China, we perform groundwater flow simulations to predict transient discharge into the long, deep-buried tunnels. Two numerical models, an equivalent porous medium model and a coupled discrete-continuum model, are used. In the coupled discrete-continuum model, both the tunnels and karst conduits are treated as discrete channels, which are coupled with the surrounding matrix through water exchange. Based on hydrogeological data and site characterization, the model parameters are calibrated by using the PEST inversion algorithm. It is shown that numerical predictions of tunnel discharge during construction agree well with the measurements, indicating reliability of the numerical models. Comparison between the two models shows that the coupled discrete-continuum model can more accurately reflect the changes in the groundwater level and can better estimate the sources of groundwater discharge into the tunnels during the construction. This work suggests that the coupled discrete-continuum model is advantageous over the equivalent porous medium model as the former is a better representation of the karst system. It is demonstrated that the simulation methodology provides a reliable method for assessment of water discharge into tunnels and the optimization of construction scheme. The results are of practical significance for safe construction of tunnels in karst areas.

Numerical Modeling of the Interference of Thermally Unbalanced Aquifer Thermal Energy Storage Systems in Brussels (Belgium)

A numerical model was built using FEFLOW® to simulate groundwater flow and heat transport in a confined aquifer in Brussels where two Aquifer Thermal Energy Storage (ATES) systems were installed. These systems are operating in adjacent buildings and exploit the same aquifer made up of mixed sandy and silty sublayers. The model was calibrated for groundwater flow and partially for heat transport. Several scenarios were considered to determine if the two ATES systems were interfering. The results showed that a significant imbalance between the injection of warm and cold water in the first installed ATES system led to the occurrence of a heat plume spreading more and more over the years. This plume eventually reached the cold wells of the same installation. The temperature, therefore, increased in warm and cold wells and the efficiency of the building’s cooling system decreased. When the second ATES system began to be operational, the simulated results showed that, even if the heat plumes of the two systems had come into contact, the influence of the second system on the first one was negligible during the first two years of joint operation. For a longer modeled period, simulated results pointed out that the joint operation of the two ATES systems was not adapted to balance, in the long term, the quantity of warm and cold water injected in the aquifer. The groundwater temperature would rise inexorably in the warm and cold wells of both systems. The heat plumes would spread more and more over the years at the expense of the efficiency of both systems, especially concerning building’s cooling with stored cold groundwater.

Post Audit of Simulated Groundwater Flow to a Short-Lived (2019 to 2020) Crater Lake at Kīlauea Volcano.

About 14.5months after the 2018 eruption and summit collapse of Kīlauea Volcano, Hawai'i, liquid water started accumulating in the deepened summit crater, forming a lake that attained 51 m depth before rapidly boiling off on December 20, 2020, when an eruption from the crater wall poured lava into the lake. Modeling the growth of the crater lake at Kīlauea summit is important for assessing the potential for explosive volcanism. Our current understanding of the past 2500 years of eruptive activity at Kīlauea suggests a slight dominance of explosive behavior over effusive. The deepened summit crater and presence of the crater lake in 2019 raised renewed concerns about explosive activity. Groundwater models using hydraulic-property data from a nearby drillhole successfully forecast the timing and rate of lake filling. Here we compare the groundwater-model predictions with observational data through the demise of the crater lake, examine the implications for local water-table configuration, consider the potential role of evaporation and recharge (neglected in previous models), and briefly discuss the energetics of the rapid boil-off. This post audit of groundwater-flow models of Kīlauea summit shows that simple models can sometimes be used effectively to simulate complex settings such as volcanoes.

Stochastic nitrate simulation under hydraulic conductivity uncertainty of an agricultural basin aquifer at Eastern Thessaly, Greece.

Lake Karla Watershed is an agricultural basin characterized by intense agricultural activities, which lead to quantitative and qualitative aquifer degradation. The exploitation of non-renewable groundwater resources and nitrate contamination are the major threats to aquifer sustainability. Groundwater resources cover mainly irrigation and domestic water needs. Hence, the simulation of groundwater resources is necessary to (a) determine the quantity available for water supply and (b) estimate probable nitrate contamination to propose subsequent remediation techniques to protect public health. Furthermore, the aquifer's heterogeneity as well as the lack of hydraulic conductivity data, in a large-scale study area, creates uncertainty regarding groundwater flow and nitrate transport simulation. Deterministic modelling approaches for spatially distributed nitrate concentration simulation could not estimate the contamination risk, since it can address only one realization of the aquifer. This study estimates the effect of hydraulic conductivity uncertainty on the simulation of groundwater nitrate concentration. The proposed framework uses Geostatistical Sequential Gaussian Simulation (SGSIM) for the generation of equally probable realizations of the spatial distribution of hydraulic conductivity. It includes the application of a modelling system based on the following inter-linked models: a rainfall-runoff model, a reservoir operation model, a lake-aquifer interaction model, a groundwater flow model, and a nitrate transport and dispersion model. The last two models simulate the multiple realizations of aquifer's groundwater flow and nitrate concentration. Furthermore, two analyses (a statistical and a threshold analysis) are employed to estimate the exceedance probability of the nitrate concentrations and their spatial extent. The results indicate that hydraulic conductivity uncertainty does affect the simulation of nitrate concentration and that nitrate concentrations will most probably exceed the thresholds in areas where groundwater is extracted for domestic use.

Integration of discrete fracture networks and flow simulator for quantification of hydrogeological uncertainty

In this study, a discrete fracture network model (DFN) and groundwater flow simulation were applied to a fractured aquifer of an open-pit mine. Conditional simulation of the fracture systems was developed to quantify and evaluate the uncertainty of geological structures and to predict possible hydrogeological risks associated with these uncertainties. The method used was based on the statistical characterization and simulation of spatial distribution scenarios of fracture lengths, directions and openings, as well as their influence on water flow behavior. The spatial configuration of the structures was generated using Poisson processes, while the lengths and angles were generated by Gaussian simulation. Flow simulation was performed with Modflow software. The resulting scenarios honored field data and quantified and evaluated the uncertainty associated with fracture distribution. In addition, the study was able to demonstrate the practical aspects of the proposed simulation method, which can then be applied to increase the planning and operational effectiveness of open-pit mines.

The importance of subsurface drainage on model performance and water balance in an agricultural catchment using SWAT and SWAT-MODFLOW

Artificial subsurface drainage impacts the hydrological system, but its spatial distribution is typically uncertain, hindering the understanding of the hydrological behaviour of a certain catchment. In this study, the effects of using four different sources to delineate the spatial distribution of subsurface drainage systems on hydrological modelling performance and simulated water balance were assessed. This work was addressed using SWAT and SWAT-MODFLOW (that is, four SWAT models and four SWAT-MODFLOW models were set up and evaluated). The spatial distribution of subsurface drainage systems were based on (1) low electrical resistivity (as a proxy for clay content) in the top 4 m of the subsurface; (2) historical maps from contractors, which conducted the drainage work; (3) settings from previous successful SWAT set-ups in Denmark; and (4) similar settings as in scenario 3, but adjusted according to the national drained area probability map in Denmark. Scenarios 1 and 4 and scenarios 2 and 3, respectively, showed similar fractions of subsurface drained areas out of the total catchment area (large and small, respectively). Scenarios 2 and 3 showed better statistical performance with SWAT, while scenarios 1 and 4 performed better using SWAT-MODFLOW. Best statistical and graphical performances were obtained with the large drain fraction scenarios and when using the coupled model. First, low drain fraction scenarios underestimated subsurface drainage flow to the stream. Besides, SWAT-MODFLOW performed better than SWAT because MODFLOW was able to simulate groundwater flow across the surface catchment, whereas SWAT by default is not capable of doing so. All things considered, impacts of different subsurface drainage scenarios on catchment hydrology are assessed using both SWAT and SWAT-MODFLOW for the first time in this work, revealing the relevance of this input step for satisfactory hydrological modelling and reinforcing previous authors findings regarding the better performance of the coupled model over SWAT, but being even more relevant in this none-zero balance catchment. The proposed method of modelling coupling, and delineating subsurface drained areas using geophysical data, is promising and can be adopted by other researchers to evaluate the water balance impact of land-use and climate changes around the world.

Assessing the Impact of Lining Polluted Streams on Groundwater Quality: A Case Study of the Eastern Nile Delta Aquifer, Egypt

Groundwater is considered to be an important water supply for domestics, industry, and irrigation in many areas of the world. Renewable groundwater is recharged by rainfall and seepage from canals and open drain networks. Agricultural and industrial drainage, as well as domestic drainage, represent the main discharges into open drains. Therefore, these drains are considered to be a source of recharge as well as a source of pollution. In this study, we aim to evaluate the impact of the Bahr El Baqar drain system on groundwater quality in the Eastern Nile Delta, Egypt. MODFLOW was used to create a numerical model to simulate groundwater flow in an aquifer and MT3DS was used to simulate solute transport from the open contaminated Bahr El Baqar drain to the groundwater. Two approaches were developed in the study area. The first approach was applied to investigate the impact of increasing the abstraction rates on the contaminant transport into the aquifer, the second approach was developed to identify the effect of lining the drain using different materials on contaminant extension in the aquifer to protect groundwater quality in the east Nile Delta Aquifer. The results showed that the TDS values increased by 18.23%, 23.29%, and 19.24% with increased abstraction rates of 15%, 34%, and 70%, resulting from population increases in 2010, 2025, and 2040, respectively; however, the TDS in the aquifer decreased from 0.6%, to 6.36%, 88.35%, and 90.47% by using lining materials.

Modelling of Groundwater Quality of Tigris River Reach-in Baghdad-Iraq Using Groundwater Modeling System Software

The effect of the industrial effluents which discharge to the Tigris River reach in Baghdad city-Iraq, from the industrial and sewage sources on the quality of groundwater was studied for the right and left sides of the flood plain of the river. There are eight sources of pollution along the Tigris River reach in which the effluent discharges were treated partially. In this study, groundwater modelling system (GMS) software (MODFLOW and MT3DMS models) was used to simulate groundwater flow and solute transport. The study area was divided into 5776 cells with a grid size of 250m × 250m with three soils. Sixteen observation wells for the water level and TDS concentrations of the groundwater were used, obtained from the Ministry of Water Resources –Iraq. The MODFLOW and MT3DMS models were calibrated and validated. The validation model was used for the simulation of the groundwater quality for the next 24 years and for three scenarios: (i) concentration of contaminants remain the same, (ii) use of full treatment for accessing the value of TDS concentration to zero, (iii) increase the effluent discharge to the double. The simulation results show an increase in the TDS concentration for all three scenarios during the next 24 years. There are no significant differences in TDS concentration during the next 24 years for the second scenario (full treatment of effluent flow). The difference in TDS concentration was about 3%. TDS concentration change is from the recharge, advection, and dispersion and diffusion process of the groundwater contaminants. When the TDS concentration of the point sources of pollution will increase to double, there is a significant difference in the TDS concentration during the next 24 years which its value was about 13% (1138-1280 ppm). There is no improvement in groundwater quality, but in all three scenarios, the quality will not meet the Iraqi standard limitation of using the groundwater during the next 24 years. The areas of the Tigris River’s left side were affected by the industrial wastewater more than the right side of the river.

Hydrogeological structure modelling based on an integrated approach using multi-source data

The simulation of groundwater flow is widely used to understand dynamic groundwater processes and frequently serves as the basis for quantitative analysis and management of groundwater resources. Reliable groundwater flow simulations require a sound understanding of the hydrogeological structure of the subsurface materials. However, a detailed model of the hydrological structure of thick unconsolidated basin sediments is often limited by their inaccessible nature, especially in the deep domain. As a result, deep regional flow is generally neglected in traditional groundwater flow simulations. This study presents an integrated approach for developing a model of hydrogeological structures using multiple data sources, including audio-magnetotelluric data (AMT), borehole data, and the interpreted lower boundary of Quaternary sediments. The approach overcomes the disadvantages of using the depth of boreholes as the lower boundary of the hydrogeological system and may be used to analyse the effects of hydrogeological structures on groundwater flow simulations. The model, which utilized sequential Gaussian simulation (SGS) and natural neighbor interpolation (NNI), was evaluated by application to a typical cross-section through the Yinchuan Basin, China, to a depth of 1,700 m. The horizontal hydraulic conductivity (Kx) field was calibrated using observation wells and the PEST pilot points (PPP) method. The effects of the developed hydrogeological structure on groundwater flow simulations were evaluated for the entire thickness of Quaternary sediments (complete-domain model, CDM) as well as for sediments above the maximum depth of the boreholes (shallow-domain model, SDM). In addition, the sensitivity of the Kx field on groundwater flow patterns was analysed. The results show that the proposed approach can characterize the spatial distribution of lithologic units and the heterogeneity of hydrogeological parameters in the deep domain (>300 m), as well as avoid the multi-solution problem of inferring hydrogeological parameters from geophysical data. It can also improve the accuracy of the hydrogeological structure model and the reliability of groundwater flow simulations. The adjustment of the hydrogeological structure affects the flow budget as well as the pattern of the groundwater flow systems (including the type of system, and their number, location, and extent). Changes in the Kx field affect the local flow field, whereas adjustment of the hydrogeological structure model affects the global flow field.

The use of the pilot points method on groundwater modelling for a degraded aquifer with limited field data: the case of Lake Karla aquifer

Abstract Groundwater depletion poses a major threat to global groundwater resources with increasing trends due to natural and anthropogenic activities. This study presents a surface-groundwater framework for water resources modelling of ill-posed problems in hydrogeologically data-scarce areas. The proposed framework is based on the application of a conceptual water balance model and composed of surface hydrological (UTHBAL) and groundwater flow simulation with the integration of a Newton formulation of the MODFLOW-2005 code (MODFLOW-NWT) and PEST suite modules. The groundwater simulation includes a preprocessor tool for automated calibration and a post-processor tool for automated validation. The methodology was applied to a rural region of Central Greece, Lake Karla Basin, which is degraded due to groundwater resources overexploitation to cover irrigation water demands. The aquifer is modelled focusing on a precise simulation–validation procedure of the conceptual model. The groundwater model was calibrated with the calibration preprocessor tool for spatially distributed hydraulic conductivity with the pilot points method. The calibration process achieved satisfactory results as validated by the post-process analysis of observed and simulated water levels. The findings for the groundwater budget indicate that the groundwater system is still under intense pressure even though farming activity in recent years has turned to less water-intensive crops. HIGHLIGHT My research deals with the pilot points method on groundwater modelling in an area with scarce hydrogeologic data.